Field of the Invention
The invention relates to a configuration for minimizing the Nxc3xa9el interaction between a first and a second ferromagnetic layer on both sides of a nonmagnetic separating layer, the first ferromagnetic layer being a sublayer of an artificial antiferromagnetic layer system. In addition, the invention relates to a configuration for compensating for a minimized Nxc3xa9el interaction in the second ferromagnetic layer.
The Nxc3xa9el interaction acts between two magnetized ferromagnetic layers on both sides of a thin, non-magnetic separating layer. It is caused by the roughness of the surfacesxe2x80x94respectively facing the separating layerxe2x80x94of the two ferromagnetic layers.
It is accordingly an object of the invention to provide a configuration for minimizing the Nxc3xa9el interaction between two ferromagnetic layers on both sides of a non-ferromagnetic separating layer, that overcomes the disadvantages of the prior art devices of this general type, in which the Nxc3xa9el interaction between the first ferromagnetic layer and the second ferromagnetic layer lying opposite the latter at the separating layer is minimized in terms of magnitude and, at the same time, the remaining Nxc3xa9el interaction is compensated for.
With the foregoing and other objects in view there is provided, in accordance with the invention, a configuration for minimizing a Nxc3xa9el interaction. The configuration contains a first asymmetrical artificial anti-ferromagnetic layer system having a first ferromagnetic sublayer, a second ferromagnetic sublayer, and a first spacer layer disposed between the first and second ferromagnetic sublayers. A separating layer is provided. The first ferromagnetic sublayer is oriented toward the separating layer and has a smaller layer thickness than the second ferromagnetic sublayer of the first asymmetrical artificial anti-ferromagnetic layer system. A second asymmetrical artificial anti-ferromagnetic layer system has a first ferromagnetic sublayer oriented toward the separating layer, a second ferromagnetic sublayer, and a second spacer layer disposed between the first and second ferromagnetic sublayers of the second asymmetrical artificial anti-ferrromagnetic layer system. The first ferromagnetic sublayer of the second asymmetrical artificial anti-ferromagnetic layer system has a smaller layer thickness than the second ferromagnetic sublayer of the second asymmetrical artificial anti-ferromagnetic layer system. Resulting total magnetizations of the first and second asymmetrical artificial anti-ferromagnetic layer systems are accumulated vectorially in a manner that compensates for the Nxc3xa9el interaction between the first ferromagnetic sublayer of the first asymmetrical artificial anti-ferromagnetic layer system and the first ferromagnetic sublayer of the second asymmetrical artificial anti-ferromagnetic layer system each being oriented toward the separating layer.
Thus, in the configuration according to the invention, a second ferromagnetic layer of a magnetoresistive memory cell with an inverse artificial antiferromagnet (AAF) reference layer system is provided as the first sublayer of a second inverse asymmetrical AAF layer system (xe2x80x9cinverse AAF memory layer systemxe2x80x9d). Such a second AAF layer system has two ferromagnetic sublayers on both sides of a second spacer layer (spacer). The first ferromagnetic sublayer, oriented toward the separating layer, of the second AAF layer system has a smaller layer thickness than the second sublayer, remote from the separating layer, of the second AAF layer system. The second AAF layer system then has in each case a net moment directed opposite to the magnetization of the first ferromagnetic sublayer, oriented toward the separating layer, of the second AAF layer system. In the case of a simplified magnetostatic consideration, the net moments of the two AAF layer systems counteract a parallel orientation of the magnetizations of the two first ferromagnetic sublayers each oriented toward the separating layer, while the remaining Nxc3xa9el interaction furthermore prefers a parallel orientation of the two magnetizations. The switching behavior of a magnetoresistive memory cell based on such a configuration can be symmetrized through suitable dimensioning of the AAF layer systems, the magnitude of the Nxc3xa9el interaction being reduced relative to conventional configurations.
The first AAF layer system (AAF reference layer system) can be coupled to a natural anti-ferromagnet in order to stabilize the magnetization. Through the coupling of the first AAF layer system to a layer made of a natural anti-ferromagnet, the magnetic stability of the AAF reference layer system is increased by a mechanism described as xe2x80x9cexchange biasingxe2x80x9d.
In accordance with an added feature of the invention, the first symmetrical artificial anti-ferromagnetic layer system is a reference layer system and the second asymmetrical artificial anti-ferromagnetic layer system is a memory layer system of a magneto-resistive memory cell. The magnetoresistive memory cell is based on a tunnel effect and the separating layer is composed of a dielectric material and functions as a tunnel barrier.
In accordance with another feature of the invention, at least one exchange bias layer is disposed at a surface of the reference layer system lying remote from the tunnel barrier and a magnetization of the exchange bias layer is fixedly coupled to a magnetization of the reference layer system. The exchange bias layer extends beyond dimensions of the reference layer system in a plane parallel to the tunnel barrier.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a configuration for minimizing the Nxc3xa9el interaction between two ferromagnetic layers on both sides of a non-ferromagnetic separating layer, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.